Hewitt said: 'This announcement is good for the environment, good for Britain's energy needs and good for jobs. The Energy White Paper committed us to providing 10 per cent of energy from renewable sources by the year 2010, and an aspiration to double that figure by the year 2020. Offshore wind has potential to provide a significant proportion of the UK's energy needs, and will help the UK renewables industry to grow, building on our world leading expertise in offshore manufacturing, creating over 20,000 new jobs in manufacturing, installation and maintenance, as the windfarms take shape.'

Three strategic areas of shallow waters have been identified by the Crown Estate and the DTI as appropriate for development: the Thames Estuary, Greater Wash, and the North West.

The sites were originally identified in November in the DTI's Future Offshore consultation, but have since been subject to rigorous environmental assessment, to assess the impact of proposed development, before sites could be offered for leasing.

Making her announcement, Hewitt asked The Crown Estate to invite windfarm developers to tender for sites in all the areas.

This will be the second round of leasing to be announced for offshore windfarm development.

The first round, which was announced in December 2000, resulted in 17 proposals from developers, two of which are already under construction: at North Hoyle, near Rhyl, and Scroby Sands near Great Yarmouth. In total Round 1 should result in more than 500 turbines, generating 1.5GW.

Round 2 is far more ambitious in scale, with each farm comprising hundreds - rather than tens of turbines. The energy produced will be sufficient to power more than 3.5million households.